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Mysterious electrical issues

NitzeyNitzey Posts: 231 Deckhand
Two starting batteries.  The  boat would not start using battery 2.  Battery 2 registered 1.1 V and so  I replaced it although it was only 2 1/2 years old.  Two weeks later the boat would not start using battery 2 again.   Voltage measured 2.2 V.  After running the boat for onlly 5 minutes,  battey 2 now measured 12.5 V.  The hookup for battery 2 is simple.  One main cable going directly to the main battery switch and one very small cable to the Mercury cathode system.   The only thing I can think of is that downstream there is some  sort of short  circuit draining battery 2.

It is even  more complicated than this, but I primarily need some ideas of what to  do next.

Replies

  • The Cat's EyeThe Cat's Eye Posts: 1,572 Captain
    edited January 2019 #2

    Seems like you cannot completely isolate the batteries when the boat is not in use , since your wiring setup has a small cable connected to the battery that bypasses the battery switch. (I assume you turn the battery switch to off when the boat is not in use?)   I would disconnect the small cable when the boat is not in use and see if your batteries stay charged. If they stay charged then you have an electrical drain in the Mercury cathode system. Then you might have to wire in another switch to isolate this system from the battery to stop the drain. 

    Of course this does not correct the problem directly. 

    Battery drains on boats used in saltwater are very common since the salt finds its way on just about every wire connection and electrical component. 


    Giimoozaabi
  • MelbourneMarkMelbourneMark Posts: 2,976 Captain
    How was the corrosion on the battery switch terminals?  Perhaps, a new switch would help.  Also, feel the battery cables and see how "flexible" they are..  If they are very stiff, then they could have gotten corrosion inside the cables themselves.  

    They make battery switches that have tinned-copper, instead of just copper.  Blue-Seas is a good name brand.  
  • NitzeyNitzey Posts: 231 Deckhand
    Perhaps it is the Mercury MerCathode system which is at fault.  The boat has a diesel engine with a Mercury outdOrive by the way.  As suggested, I can disconnect the small wire (actually it has a fuse and so can just take the fuse out) and see if the problem goes away.  Of course whatever ails the MerCathode system, if it is at fault, needs to be fixed.

    Prior to this I replaced the main battery switch.  I convinced Bluesea to send me a new one, but now I think there was nothing wrong with the old one.  The old one looked great although it was 13 years old.
  • SansPeurSansPeur Orlando, FLPosts: 162 Deckhand
    edited January 2019 #5
    Remove the positive cable from the battery . Take a volt meter and set it to measure the amps. Put the positive leed on the battery terminal and then use the negative leed to see if the cable or the mercathode is pulling amps. It should be clear which is the culprit at that point.
    Since 2004 as ReelDreams.
  • NitzeyNitzey Posts: 231 Deckhand
    SansPeur said:
    Remove the positive cable from the battery . Take a volt meter and set it to measure the amps. Put the positive leed on the battery terminal and then use the negative leed to see if the cable or the mercathode is pulling amps. It should be clear which is the culprit at that point.
    This makes sense.  If amperage is high enough to read on my meter, then It should indeed be clear.  

    Meanwhile what I  did today is install a  new battery and disconnect the Merthcathode system.  I will check Monday to see if the new battery maintained its charge or was drained.  I will  also try your approach.
  • NitzeyNitzey Posts: 231 Deckhand
    Took photos yesterday of corrosion protection system.  Noticed today, one side looks suspicious.
  • DOCKSIDEDOCKSIDE Posts: 1,897 Captain
    Nitzey said:
    Took photos yesterday of corrosion protection system.  Noticed today, one side looks suspicious.
    um, yep....
    somewhere south of disorder and on earth... mostly .
    ..............................................................................
    IBEW LU 433
  • NitzeyNitzey Posts: 231 Deckhand
    Furthermore measured 12.88 V today. So, think case solved. Ordered new controller, $92
  • StankBaitStankBait Posts: 415 Deckhand
    Had a mercathode and it would draw down batteries. Disconnected when not in the water. The unit may be fried but mine was not and had to disconnect to stop battery drain.
  • NitzeyNitzey Posts: 231 Deckhand
    StankBait said:
    Had a mercathode and it would draw down batteries. Disconnected when not in the water. The unit may be fried but mine was not and had to disconnect to stop battery drain.
    You might give Mercury a call, (920) 929 5040.  If you still have this unit, they might send you a new one.  According to their book, it should take only a tiny current to work effectively.
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